Sealed cells have been widely used for a long time in consumer electrical appliances, and recently, in particular, lithium cells have become very widely used. Since the energy density of lithium cells is high, their development as a power source for electric automobiles (EVs) and hybrid automobiles (HEVs) has progressed remarkably, and they are now required to conduct high electrical currents. For this purpose, with lithium cells, countermeasures have been developed for lowering the resistance of various components, in particular welding together a top cover and a diaphragm (a top cover casing) of a lid unit (a sealing lid) (refer to Patent Document #1) and so on.